Help with sick Muscovy Drake

HI
My 3yr old Muscovy Drake Rubber has been very quiet and lethargic for the past couple of days, he has been hiding himself in the spare room which is very unusual normally he prefers to spend the day outside which the other ducks and he only comes in at night, his not talking to me like he usually does and he has been pooping mostly water since Thursday in some cases yesterday only water although he did do a more normal poop today after I gave him some peas. He has also been panting today although he has plenty of water and its not hot. I took him to the local vet as I was worried about heavy metal poisoning. I saw 2 different vets the first one told me he had a temperature and the only thing they could do was take an x-ray to see if he had any metal in his stomach and that they didn't do blood tests to check for heavy metal poisoning. The 2nd vet told me that he didn't have a temperature and said he could see no metal in his stomach but the was something there that could either be something he was trying to pass or it could be a tumour he didn't know as he didn't know anything about ducks. I was told to give him some antibiotics its called Bactrim and is sulfamethoxazole and trimethoprim at 1ml for every kg twice a day (he is 5kg) just in case he has a bacterial infection. The closest avian vet is 3 1/2 hours away and I don't have a car if( I did I would take him) although I have emailed them I'm not hopeful of a reply. The local vets have no idea about ducks (as they told me in those exact words after I paid them $200 for the privilege) and are unwilling to look in to it further. Rubber is very much my baby and I am desperate to make sure he is ok. I was wondering if anyone has any ideas on what his problem could be. I have included the x-ray pictures (that my husband was smart enough to get them to email to us) incase anyone can make sense of them for me. The vet didn't know what he was looking at and said so. Any help would be very much appreciated.